Return the match for key in map mapname, or raise an error
(nis.error) if there is none. Both should be strings, key is 8-bit
clean. Return value is an arbitrary array of bytes (may contain NULL and
other joys).

Note that mapname is first checked if it is an alias to another name.

The domain argument allows to override the NIS domain used for the lookup. If
unspecified, lookup is in the default NIS domain.